In recent years a technique known as near-infrared fluorescent imaging has been used in surgical procedures. In this near-infrared imaging, indocyanine green (ICG) has been injected, as a fluorescent dye into a tissue to be examined. Given this, when the indocyanine green is illuminated with near-infrared radiation of a wavelength of about 810 nm (nanometers), as excitation radiation, the indocyanine green emits near-infrared fluorescence at a wavelength of approximately 845 nm. This fluorescence is picked up by an imaging element that is able to detect near-infrared radiation, and an image thereof is displayed on a displaying portion such as a liquid crystal display panel, or the like. This near-infrared fluorescent imaging makes it possible to observe blood vessels, lymph ducts, and the like that exist to a depth of about 20 mm from the surface of the body.
This type of near-infrared fluorescent imaging is used in, for example, surgical procedures on tumors. For example, when performing a procedure for mammary cancer in surgery on a mammary gland, it is necessary to determine the position of the sentinel lymph node. This sentinel lymph node is the lymph node wherein the cancerous cells that are carried by the lymph flow first arrive. If no cancerous cells are discovered in the sentinel lymph node, then it can be concluded that the mammary cancer has not spread to the lymph nodes of the armpit region. The use of near-infrared fluorescent imaging in order to identify the location of the sentinel lymph node is effective for this purpose.
Moreover, in the same way, when carrying out a procedure for gastric cancer in abdominal surgery, the stage of cancer can be ascertained by the degree of spread to the lymph nodes in the region. Because the course of treatment will vary depending on the stage of cancer, it is possible to prevent overly aggressive treatment or insufficient treatment in advance through an evaluation of whether or not the cancer has spread to the lymph nodes in the region. Ascertaining the locations of the lymph nodes in the region through near-infrared fluorescent imaging is effective in this case as well.
Patent Document 1 discloses a data collecting method wherein an intensity distribution image of near-infrared fluorescence, obtained through exposing, to indocyanine green excitation radiation, an organ for in-vivo examination into which indocyanine green has been injected, with a carcinomatous lesion distribution image that has been obtained through the use of x-rays, nuclear magnetic resonance, or ultrasound on the organ prior to injection of the indocyanine green, to collect, as regional data for the tissue surrounding the cancer, data for regions that can be detected through the intensity distribution image of the near-infrared fluorescence but cannot be detected through the carcinomatous lesion distribution image.